Chip Somodevilla/Getty Images(WASHINGTON) -- The Gang of Eight immigration bill does not yet have a 60-vote majority in the Senate, according to one of its authors, Sen. Bob Menendez.

During an interview with Univision's Jorge Ramos, Menendez, D-N.J., appeared confident that Congress will pass a comprehensive immigration reform bill. But he said the Senate bill's backers haven't yet cobbled together a large enough majority to avoid a potential filibuster.

"We don't currently have 60 votes identified in the Senate," he said during the interview with Ramos, which was conducted in Spanish for Al Punto, Univision's Sunday public affairs show. "We need to add more votes on the floor."

Menendez's comments are surprising, considering the positive outlook of the bill's supporters this week. On Tuesday, the Senate Judiciary Committee passed the legislation on a bipartisan 13-5 vote, encouraging the bill's backers that they could attract a majority on the Senate floor.

"This is a significant first step, and there will be more tests to come, but this accomplishment makes me guardedly optimistic for the success of the legislation," Sen. John McCain, R-Ariz., one of the bill's authors, said in a statement after the committee vote.

Menendez's assessment might not carry such a dire warning in the short term. Senate Minority Leader Mitch McConnell, R-Ky., has said that he will not block the immigration bill from coming to the floor, despite opposition from some conservative members and activists. But the bill could face a filibuster if and when leaders move it to a final vote.

Plus, leading members of the Gang of Eight have set a high target for the level of support they hope to lure; 70 votes, pulling from majorities of both Democrats and Republicans in the upper chamber.

A strong majority of 70 votes, they believe, is not only possible but necessary to cajole the Republican-controlled House of Representatives to act. Despite his evaluation of the current level of support, Menendez believes that is possible.

"We want to push this bill forward with the most positive votes we can find … so we can put pressure on the House," he said. "I want to have a good vote in the Senate so we send the message that the Republicans and the Democrats are together in favor of immigration reform."

Menendez framed his projection about the votes as a call to action for Latino supporters of the bill. He urged them to call their members of Congress to build the support necessary for the legislation to pass.

"The community in your state, in every state, should be contacting your state's two U.S. senators saying that they want comprehensive immigration reform, that they are going to judge their political future based on this vote," he said. "And if we do this, both in the Senate and, later, with the members of the House of Representatives, we can achieve the victory that we want."